High Pressure Processing Pressure Sensor

ABSTRACT

A pressure sensor and its use for visually determining whether a preselected pressure threshold has been achieved, for example during high pressure processing treatment of a foodstuff. The pressure sensor includes a contained color-changing system having a dye, a developer, and a solvent; upon achievement of the preselected pressure threshold, the dye and the developer interact, resulting in a visible color change. Further, the visible color change can be retained upon a decrease in pressure and upon an increase in temperature, thereby effectively recording the achievement of the preselected pressure threshold during the high pressure processing treatment.

I. SUMMARY OF THE INVENTION

A broad object of a particular embodiment of the invention can be toprovide a pressure sensor including a contained color-changing systemhaving a dye, a developer, and a solvent, whereby the developer variablyinteracts with the dye according to the pressure of the color-changingsystem. Upon achievement of a pressure threshold, the dye and thedeveloper interact, resulting in a visible color change. Further, thevisible color change can be retained upon a decrease in pressure andupon an increase in temperature, thereby effectively recording theachievement of the pressure threshold.

Another broad object of a particular embodiment of the invention can beto provide a method of using the pressure sensor (i) for visuallydetermining whether a pressure threshold has been achieved during highpressure processing treatment of a foodstuff, or (ii) for indicatingachievement of a pressure threshold during high pressure processingtreatment of a foodstuff, whereby the method includes reliablyassociating the pressure sensor with a foodstuff. Further, the methodcan, but need not necessarily, include subjecting the foodstuff to highpressure processing treatment. Further, the method can, but need notnecessarily, include detecting whether or not the visible color changeoccurred. As to particular embodiments, detecting whether or not thevisible color change occurred can include visually observing thepressure sensor.

Naturally, further objects of the invention are disclosed throughoutother areas of the specification, drawings, photographs, and claims.

II. A BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is an illustration of a particular embodiment of the instantpressure sensor reliably associated with a foodstuff prior to HPPtreatment and correspondingly, prior to exposure to a preselectedpressure threshold, whereby the color-changing system of the pressuresensor has not undergone a visible color change.

FIG. 1B is an illustration of the particular embodiment of the instantpressure sensor shown in FIG. 1A upon HPP treatment and correspondingly,upon exposure to a preselected pressure threshold, whereby thecolor-changing system of the pressure sensor has undergone a visiblecolor change.

FIG. 1C is an illustration of the particular embodiment of the instantpressure sensor shown in FIG. 1B following depressurization after HPPtreatment to atmospheric pressure, whereby the color-changing system ofthe pressure sensor retains the visible color change.

FIG. 2A is a cross sectional view through a particular embodiment of theinstant pressure sensor reliably associated with a foodstuff prior toHPP treatment and correspondingly, prior to exposure to a preselectedpressure threshold, whereby the dye and the developer are not complexedand thus, the color-changing system of the pressure sensor has notundergone a visible color change.

FIG. 2B illustrates the particular embodiment of the instant pressuresensor shown in FIG. 2A upon HPP treatment and correspondingly, uponexposure to a preselected pressure threshold, whereby achievement of thepreselected pressure threshold facilitates formation of a visiblycolored dye-developer complex which provides a visible color change.

FIG. 2C illustrates the particular embodiment of the instant pressuresensor shown in FIG. 2B following depressurization after HPP treatmentto atmospheric pressure, whereby the visibly colored dye-developercomplex is stably retained and thus, continues to provide the visiblecolor change.

FIG. 3 is an illustration of hysteresis characteristics of a particularembodiment of the instant thermochromic color-changing system which hasa color-memory property.

FIG. 4 is a photograph of experimental results obtained after subjectingfive instant pressure sensor samples to HPP treatments of varyingpreselected pressure thresholds.

III. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Now referring primarily to FIG. 1A through and FIG. 1C, which illustratea method of using a particular embodiment of the inventive pressuresensor (1) for visually determining whether a preselected pressurethreshold has been achieved or for indicating achievement of apreselected pressure threshold, whereby the pressure sensor (1) includesa contained color-changing system (2) comprising: a dye (3), a developer(4), and a solvent (5). The developer (4) variably interacts with thedye (3) according to the pressure of the color-changing system (2),whereby upon achievement of the preselected pressure threshold, the dye(3) and the developer (4) interact, resulting in a visible color change(6) which can be detected or visually observed.

Now referring primarily to FIG. 2A through and FIG. 2C, to elaborate onthe above, interaction between the dye (3) and the developer (4) resultsin the formation of a visibly colored dye-developer complex (7) whichcan be detected or visually observed to indicate that the preselectedpressure threshold has been achieved.

Accordingly, the method of use can include detecting whether or not thevisible color change occurred, for example by visually observing thepressure sensor (1), whereby visual detection of the visible colorchange (6) resulting from the formation of the visibly coloreddye-developer complex (7) indicates that the preselected pressurethreshold has been achieved. Conversely, visual detection of the absenceof the visible color change (6), meaning no visible color changeoccurred, indicates that the preselected pressure threshold has not beenachieved.

High Pressure Processing

The instant pressure sensor (1) may be particularly useful for detectingand signaling that a desired pressure, referred to as the preselectedpressure threshold, has been achieved within a vessel (8) such as afood-processing vessel (8). In a particularly desirable application, thevessel (8) is a pressurization vessel (8) used in high pressureprocessing (HPP) methods for reducing the threat posed by microbialcontamination of foodstuff (9).

HPP food-processing methods are well known and described by others.Although HPP methods are known to be effective for enhancing themicrobial safety of treated foodstuff (9), they have the significantdrawback that HPP-treated foodstuff (9) and its associated packagingoften have the same appearance before and after HPP treatment. Failureor improper operation of HPP equipment can yield foodstuff (9) which maybe unsafe for consumption but has the appearance of HPP-treatedfoodstuff (9), even though it has not been so treated. Thus, one storingor using untreated foodstuff (9) may fail to appreciate the microbialrisk present in the foodstuff (9), potentially resulting in seriousillness, injury, or death. For this reason, stringent attention is oftenpaid to product traffic control in HPP methods, to ensure that theHPP-treatment status of foodstuff (9) is accurately monitored. Suchtraffic control methods impose significant effort and expense, and maynevertheless fail to ensure that appropriate contamination-reductionmethods have been employed. What is needed is an indicator that (i) canaccompany foodstuff (9) throughout an HPP treatment regimen (i.e., suchthat the indicator undergoes the same treatment as the foodstuff (9)),and (ii) indicate whether the preselected pressure threshold has beenachieved in the vessel (8) containing the foodstuff (9) and theindicator. The instant disclosure provides such an indicator configuredas a pressure sensor (1) and methods of using the pressure sensor (1),whereby the pressure sensor (1) can be reliably associated with thefoodstuff (9) undergoing HPP treatment.

Numerous methods of reliably associating an indicating device withfoodstuff (9) undergoing processing are known (e.g., devices andmechanisms for adhering, tying, bundling, hanging, wrapping, stuffing,mixing, interleaving, or co-packaging devices and foodstuff (9) on, to,from, or with one another or on, to, from, or with common racks,packages, pallets, and the like) and can be used to reliably associatethe pressure sensor (1) described herein with one or more foodstuffs (9)for co-processing via HPP treatment.

Advantageously, the pressure sensor (1) and methods described hereinprovide a convenient, preferably direct visual, indication orconfirmation that a foodstuff (9) subjected to HPP treatment has beensubjected to the preselected pressure threshold. This relatively simplemeans of confirmation reduces the need for cumbersome and expensivemethods of providing traffic control for HPP-treated foodstuff (9), andcan prevent unintentional bypass of HPP treatment.

Definitions

As used herein, the term “sensor” means a composition or an apparatuswhich detects or measures a stimulus and reacts to it in a particularway.

As used herein, the term “contained” indicates that the dye (3), thedeveloper (4), and the solvent (5) are continuously kept within aphysical proximity which allows interaction between the compounds.Additionally, by being contained, the color-changing system (2) isseparated from the external environment, which may damage or destroy thecolor-changing system (2).

As used herein, the term “preselected” means predetermined or decided inadvance.

As used herein, the term “threshold” means the point which must beobtained or exceeded for a certain phenomenon to occur or be manifested.

As used herein, the term “dye” means a chemical compound which canchange color, such as a color former which is capable of reacting withthe instant developer (4) to form a dye-developer complex (7) whichexhibits optical properties that can be discerned by the human eye.

As used herein, the term “developer” means a chemical compound which iscapable of reacting with the instant dye (3) to form a dye-developercomplex (7) which exhibits optical properties that can be discerned bythe human eye. The term “developer” can be synonymous with “colordeveloper”, both meaning a chemical compound which facilitates a changein color of the dye (3).

As used herein, the term “solvent” can, but need not necessarily, besynonymous with phase-change material, whereby phase-change material isherein defined simply as a material which changes from one phase toanother.

As used herein, the term “foodstuff” means a good, item, or article thatis consumable (including edible or drinkable) or is useful as aningredient for making a consumable item or article. Non-limitingexamples of foodstuffs (9) include fruits, juices, vegetables, grains,flours, milks, yogurts, sweetened beverages, meats, processed foods,medicaments, and the like.

As used herein, the term “detect” and forms thereof means to discover orascertain the presence of.

Two objects, such as a foodstuff (9) and the instant pressure sensor(1), subjected to HPP treatment are “reliably associated” if theassociation between the two objects can be expected not to be disruptedby subjecting the reliably associated objects to the HPP treatment.Non-limiting examples of such reliable associations include adhering oneobject to another, tying the two objects together, containing bothobjects in a container, printing one object (for example the pressuresensor (1) configured as a printing ink) on packaging material or acontainer used to contain the other object (for example the foodstuff(9)), affixing one object (for example the pressure sensor (1)) topackaging material or a container used to contain the other object (forexample the foodstuff (9)), and laminating one object (for example thepressure sensor (1)) in a portion of a packaging material used toenclose the other object (for example the foodstuff (9)).

Pressure Sensor-Foodstuff Assembly

As stated above, the instant disclosure provides a pressure sensor (1)for use together with one or more foodstuffs (9) in an HPP method.

In an important embodiment, the instant disclosure relates to anassembly for indicating achievement of the preselected pressurethreshold in an HPP method for treating a foodstuff (9), whereby theassembly includes the foodstuff (9) reliably associated with thepressure sensor (1) described herein, as shown in FIG. 1A through FIG.2C.

HPP equipment typically uses a working fluid, most commonly water. Suchequipment generally includes a pressure chamber such as a vessel (8)into which a foodstuff (9) or the instant assembly can be placed. Afterloading (i.e., placement of the foodstuff (9) or the instant assemblywithin the vessel (8)), the vessel (8) is filled with the working fluid,and the vessel (8) is pressurized by application of a high hydrostaticpressure (e.g., about 29,000 psi to about 145,000 psi, more typicallyabout 29,000 psi to about 87,000 psi) to the working fluid.

Because pressure within the working fluid in the vessel (8) is uniformthroughout the working fluid, and because the working fluid in anoperating HPP apparatus completely surrounds the foodstuff (9) or theinstant assembly, the hydrostatic pressure within the vessel (8) isapplied isotropically (i.e., not in any particular direction more thananother) to the foodstuff (9) or the instant assembly. So long as thefoodstuff (9) or the instant assembly does not contain compressiblematerials (e.g., gases such as air bubbles, as water and other fluidstend to be substantially incompressible at HPP pressures), the shape ofthe foodstuff (9) or the instant assembly tends not to be alteredsignificantly (even though some microscopic changes may occur, such asdenaturation of proteins within the foodstuff (9)). Furthermore,foodstuff (9) that does not include portions capable of withstandingdeformation at the preselected pressure threshold will also transmit thepressure within the foodstuff (9), the result being that the hydrostaticpressure applied to the vessel (8) occurs throughout the treatedfoodstuff (9) or the instant assembly.

Maintenance of the foodstuff (9) at the preselected pressure thresholdresults in damage to microorganisms (e.g., bacteria, mold, yeast,parasites, or the like) that may be present on or within the foodstuff(9). Regardless of the precise nature of the damage, microorganismssubjected to HPP treatment appear to replicate and metabolize atsubstantially lower rates than non-HPP-treated microorganisms. Thiseffect is the primary basis for the desirability of HPP treatment offoodstuff (9).

Pressure Sensor

Simply summarized again, and as shown in FIG. 1A through FIG. 2C, thepressure sensor (1), which may take the form of a composition or anapparatus, includes a contained color-changing system (2) comprising adye (3), a developer (4), and a solvent (5). The developer (4) variablyinteracts with the dye (3) according to the pressure of thecolor-changing system (2), whereby upon achievement of the preselectedpressure threshold, the dye (3) and the developer (4) interact,resulting in a visible color change (6) which can be detected orvisually observed.

Dye and Developer

The instant color-changing system (2) can be a reversible color-changingsystem, meaning that the visible color change can be reversible, asopposed to an irreversible color change or a permanent color change.

Following, as to particular embodiments, the dye (3) of the instantcolor-changing system (2) can comprise a leuco dye (3) which canreversibly change between two forms, one of which is typically colorlessor substantially colorless.

As but only a few non-limiting examples for the purpose of illustration,the leuco dye (3) can be: crystal violet lactone (CAS No.: 1552-42-7);Pigment Blue 63 (CAS No.: 16521-38-3);2′-(dibenzylamino)-6′-(diethylamino)fluoran (CAS No.: 34372-72-0); orthe like.

As to particular embodiments, the leuco dye (3) can be anelectron-donating compound (or proton-accepting compound). Further, thedeveloper (4) can comprise an electron-accepting compound (orproton-donating compound), such as an acid and particularly, a weakacid. Upon interaction (specifically, an electron transfer reaction)between the electron-donating leuco dye (3) and the electron-acceptingdeveloper (4), the leuco dye (3) reversibly changes color, for examplefrom a colorless or substantially colorless state to a visibly coloredstate.

As but only a few non-limiting examples for the purpose of illustration,the developer (4) can be: 3,5-di-tert-butylcatechol (CAS No.:1020-31-1); 4,4′-(1,3-dimethylbutylidene)diphenol (CAS No.: 1020-31-1);2,2′-biphenol (CAS No.: 1806-29-7); or the like.

Without being bound by any particular theory of operation, it isbelieved that within the instant color-changing system (2), uponachievement of the preselected pressure threshold, the developer (4)reversibly interacts with the leuco dye (3) via an electron transferreaction to open up the lactone ring of the leuco dye (3) and stabilizethe opened structure, forming a supramolecular visibly coloreddye-developer complex (7), to which the visible color change (6) isattributable. When open, the lactone ring is cationic in nature, therebyextending conjugation of its π electrons and allowing absorption in thevisible spectrum to provide the visibly colored dye-developer complex(7), whereby the stability of the visibly colored dye-developer complex(7) is determined, at least in part, by the affinity of the developer(4) for the leuco dye (3).

Solvent

The instant color-changing system (2) further includes a solvent (5)which effects or controls the reversible interaction between the leucodye (3) and the developer (4).

As to particular embodiments, a solvent (5) which may be useful for theinstant color-changing system (2) can be (i) a solvent (5) in which boththe dye (3) and the developer (4) are soluble, and (ii) a solvent (5)which is capable of being contained along with the dye (3) and thedeveloper (4), for example within a capsule or microcapsule (10) toprovide a corresponding encapsulated or microencapsulated color-changingsystem (11). When contained within the capsule or microcapsule (10), thesolvent (5) can facilitate the interaction between the leuco dye (3) andthe developer (4).

As to particular embodiments, the solvent (5) can be a hydrocarbon.

As to particular embodiments, the solvent (5) can be a ketone.

As to particular embodiments, the ketone can have formula I as follows:

As to particular embodiments, the ketone can have formula I, whereby R′and R″ can be either the same or different, and R′ and R″ can be (i) astraight-chain, branched, or cyclic alkyl group, (ii) a straight-chain,branched, or cyclic alkenyl group, (iii) a straight-chain, branched, orcyclic alkynyl group, (iv) an aryl group, or (v) a heteroaryl group,whereby any of the groups can be unsubstituted or substituted.

As to particular embodiments, the solvent (5) can be an ester.

As to particular embodiments, the ester can have formula II as follows:

As to particular embodiments, the ester can have formula II, whereby R′and R″ can be either the same or different, and R′ and R″ can be (i) astraight-chain, branched, or cyclic alkyl group, (ii) a straight-chain,branched, or cyclic alkenyl group, (iii) a straight-chain, branched, orcyclic alkynyl group, (iv) an aryl group, or (v) a heteroaryl group,whereby any of the groups can be unsubstituted or substituted.

As to particular embodiments, the solvent (5) can be an alcohol.

As to particular embodiments, the alcohol can be an aliphatic alcohol,an aromatic alcohol, or combinations thereof.

As to particular embodiments, the solvent (5) can be a single compound.

As to other particular embodiments, the solvent (5) can be a mixture oftwo or more compounds. As to particular embodiments, the solvent (5) canbe a mixture of two or more of the illustrative solvents (5) describedabove.

Without being bound by any particular theory of operation, it isbelieved that within the instant color-changing system (2), thedeveloper (4) can also interact with the solvent (5) to form asolvent-developer complex, whereby this interaction is determined, atleast in part, by the affinity of the developer (4) for the solvent (5).

Following, it may be hypothesized that the visible color change (6) canbe linked to a competition between the leuco dye (3) and the solvent (5)for complexing with the developer (4), whereby the developer (4) forms acomplex with the molecule(s) which it has a greater affinity for.

It should be understood that once a complex forms, the complex is stableuntil an amount of energy which is sufficient to destabilize the complexis input into the system, thereby dissociating the components of thecomplex.

Relating to the instant pressure sensor (1), at pressures lesser than orbelow the preselected pressure threshold, such as at atmosphericpressure, the developer (4) can have a greater affinity for the solvent(5) than for the leuco dye (3) and accordingly, the solvent-developercomplex can be favored over the visibly colored dye-developer complex(7). Thus, the developer (4) is precluded from interacting with theleuco dye (3) to produce the visible color change and correspondingly,the lactone ring is closed and the leuco dye (3) is colorless orsubstantially colorless at pressures lesser than or below thepreselected pressure threshold.

Conversely, upon achievement of the preselected pressure threshold, thedeveloper (4) has a greater affinity for the leuco dye (3) than for thesolvent (5); hence, the visibly colored dye-developer complex (7) isformed and stabilized, producing the visible color change (6).

Color Memory

As described above, the instant color-changing system (2) can besusceptible to a pressure-modulated color change. Furthermore, theinstant color-changing system (2) can have a color-memory propertywhereby after the visibly colored dye-developer complex (7) is formedupon achievement of the preselected pressure threshold, the visiblycolored dye-developer complex (7) remains stable upon a decrease inpressure from the preselected pressure threshold, for example to apressure lesser than or below the preselected pressure threshold,including at atmospheric pressure; hence, the visible color change (6)can be retained at pressures lesser than or below the preselectedpressure threshold. Correspondingly, the pressure sensor (1) caneffectively record the achievement of the preselected pressurethreshold, which is in contrast to conventional pressure indicators,which may only indicate the current pressure and may not indicatepressures which the pressure indicator was exposed to prior to exposureto the current pressure.

In addition to being susceptible to a pressure-modulated color change,the instant color-changing system (2) can be a thermochromiccolor-changing system (2) which can be susceptible to atemperature-modulated color change.

As to particular embodiments, the instant thermochromic color-changingsystem (2) can be a reversible thermochromic color-changing system (2),whereby the temperature-modulated color change can be reversible, asopposed to an irreversible color change or a permanent color change.

The instant reversible thermochromic color-changing system (2) can havea color-memory property whereby after the visibly colored dye-developercomplex (7) is formed upon achievement of the preselected pressurethreshold, the visibly colored dye-developer complex (7) remains stable(i) upon a decrease in pressure from the preselected pressure thresholdand (ii) upon an increase in temperature; hence, the visible colorchange (6) can be retained. Correspondingly, the pressure sensor (1) caneffectively record the achievement of the preselected pressure thresholdeven upon an increase in temperature.

The color-memory property of the instant reversible thermochromiccolor-changing system (2) can be imparted, at least in part, by asolvent (5) which is pressure-sensitive and condenses in volume upon anincrease in pressure. Without being bound by any particular theory ofoperation, it is believed that an increase in pressure alters thecoloration temperature of the reversible thermochromic color-changingsystem (2). For example, upon an increase in pressure, the colorationtemperature of the reversible thermochromic color-changing system (2)correspondingly increases.

Thus, the instant reversible thermochromic color-changing system (2) caninclude a coloration temperature at which the reversible thermochromiccolor-changing system (2) changes from a substantially colorless stateto a visibly colored state. Also, the instant reversible thermochromiccolor-changing system (2) can include a decoloration temperature atwhich the reversible thermochromic color-changing system (2) changesfrom the visibly colored state to the substantially colorless state.

Significantly, the coloration and decoloration temperatures of theinstant reversible thermochromic color-changing system (2) can bedifferent, meaning that the coloration temperature can be discrete fromthe decoloration temperature. For example, the coloration temperaturecan be less than the decoloration temperature.

Consequently, the color-memory property of the instant reversiblethermochromic color-changing system (2) can facilitate retention of thevisible color change upon an increase in temperature from the colorationtemperature to a temperature greater than or above the colorationtemperature. Additionally, the color-memory property of the instantreversible thermochromic color-changing system (2) can facilitateretention of the visibly colored state upon an increase in temperaturefrom the coloration temperature to a temperature greater than or abovethe coloration temperature.

As to particular embodiments, the coloration temperature can differ fromthe decoloration temperature by at least about 10 Celsius degrees,meaning that the decoloration temperature can be at least about 10Celsius degrees greater than the coloration temperature.

As to particular embodiments, the coloration temperature can differ fromthe decoloration temperature by at least one selected from the groupincluding or consisting of: at least about 5 Celsius degrees, at leastabout 10 Celsius degrees, at least about 15 Celsius degrees, at leastabout 20 Celsius degrees, at least about 25 Celsius degrees, at leastabout 30 Celsius degrees, at least about 35 Celsius degrees, at leastabout 40 Celsius degrees, at least about 45 Celsius degrees, at leastabout 50 Celsius degrees, at least about 55 Celsius degrees, at leastabout 60 Celsius degrees, at least about 65 Celsius degrees, at leastabout 70 Celsius degrees, at least about 75 Celsius degrees, at leastabout 80 Celsius degrees, at least about 85 Celsius degrees, at leastabout 90 Celsius degrees, at least about 95 Celsius degrees, at leastabout 100 Celsius degrees, and greater than about 100 Celsius degrees.

As to particular embodiments, the coloration temperature can beassociated with the freezing point of the reversible thermochromiccolor-changing system (2). Accordingly, the instant reversiblethermochromic color-changing system (2) can include (i) a freezing pointat which the reversible thermochromic color-changing system (2) changesfrom a substantially colorless state to a visibly colored state.Moreover, the instant reversible thermochromic color-changing system (2)can include a melting point at which the reversible thermochromiccolor-changing system (2) changes from the visibly colored state to thesubstantially colorless state.

Significantly, the freezing and melting points of the instant reversiblethermochromic color-changing system (2) can be different, meaning thatthe freezing point can be discrete from the melting point. For example,the freezing point can be less than the melting point.

Consequently, the color-memory property of the instant reversiblethermochromic color-changing system (2) can facilitate retention of thevisible color change upon an increase in temperature from the freezingpoint to a temperature greater than or above the freezing point.Additionally, the color-memory property of the instant reversiblethermochromic color-changing system (2) can facilitate retention of thevisibly colored state upon an increase in temperature from the freezingpoint to a temperature greater than or above the freezing point.

As to particular embodiments, the freezing point can differ from themelting point by at least about 10 Celsius degrees, meaning that themelting point can be at least about 10 Celsius degrees greater than thefreezing point.

As to particular embodiments, the freezing point can differ from themelting point by at least one selected from the group including orconsisting of: at least about 5 Celsius degrees, at least about 10Celsius degrees, at least about 15 Celsius degrees, at least about 20Celsius degrees, at least about 25 Celsius degrees, at least about 30Celsius degrees, at least about 35 Celsius degrees, at least about 40Celsius degrees, at least about 45 Celsius degrees, at least about 50Celsius degrees, at least about 55 Celsius degrees, at least about 60Celsius degrees, at least about 65 Celsius degrees, at least about 70Celsius degrees, at least about 75 Celsius degrees, at least about 80Celsius degrees, at least about 85 Celsius degrees, at least about 90Celsius degrees, at least about 95 Celsius degrees, at least about 100Celsius degrees, and greater than about 100 Celsius degrees.

Now referring primarily to FIG. 3, hysteresis characteristics of aparticular embodiment of the instant reversible thermochromiccolor-changing system (2) having the color-memory property can bedescribed by illustrating the dependence of color density on temperaturewhereby as stated above, it is herein instantly recognized that thecoloration temperature of the reversible thermochromic color-changingsystem (2) can be altered by pressure and in particular, the colorationtemperature increases upon an increase in pressure.

Again referring primarily to FIG. 3, the y axis shows the color densityand the x axis shows the temperature. The color density of thereversible thermochromic color-changing system (2) changes withtemperature along the curve in the direction shown by the arrow marks.Point A indicates the color density at the maximum temperature T₁ forachieving the completely colored state (whereby T₁ is the completecoloration temperature). Point B indicates the color density at themaximum temperature T₂ for retention of the completely colored state(whereby T₂ is the decoloration initiation temperature). Point Cindicates the color density at the minimum temperature T₃ for achievinga completely decolored or colorless state (whereby T₃ is the completedecoloration temperature). Point D indicates the color density at theminimum temperature T₄ for retention of the completely decolored orcolorless state (whereby T₄ is the coloration initiation temperature).

Again referring primarily to FIG. 3, while both the completely coloredstate and the completely decolored or colorless state can exist betweenT₂ and T₄, the state retained is dependent upon the state previouslyachieved. For example, if the completely colored state was previouslyachieved upon exposure to T₁, the completely colored state will beretained until exposure to a temperature equal to or greater than T₂.Alternatively, if the completely decolored or colorless state waspreviously achieved upon exposure to T₃, the completely decolored orcolorless state will be retained until exposure to a temperature equalto or lesser than T₄.

As to particular embodiments, the colored state or the decolored orcolorless state can be retained upon exposure to temperatures betweenabout 5 Celsius degrees to about 100 Celsius degrees from thetemperature at which the colored state or the decolored or colorlessstate was achieved. Said another way, the length of segment EF shown inFIG. 3, which represents the temperature range width indicating thedegree of hysteresis or hysteresis range or hysteresis window ΔH, can bein a range of between about 5 Celsius degrees to about 100 Celsiusdegrees.

As but one illustrative example relating to HPP, upon achievement of thepreselected pressure threshold, the thermochromic color-changing system(2) can undergo a visible color change (6) and be completely colored atT₁. Following, the completely colored state can be retained upon adecrease in pressure, for example upon a decrease in pressure toatmospheric pressure. Further, the completely colored state can beretained upon heating, as the visibly colored dye-developer complex (7)remains stable until temperature T₂ is reached.

As to particular embodiments, T₁ may, but need not necessarily, be atemperature lesser than about 20° Celsius. For example, T₁ may, but neednot necessarily, be a temperature between about −30° Celsius to about20° Celsius.

As to particular embodiments, T₂ may, but need not necessarily, be atemperature greater than about 30° Celsius. For example, T₂ may, butneed not necessarily, be a temperature between about 30° Celsius toabout 90° Celsius.

Phase Change Material

As to particular embodiments, the solvent (5) can be a phase changematerial which changes between a liquid phase (or a substantially liquidphase) and a solid phase (or a substantially solid phase) according tothe pressure of the color-changing system (2).

As to particular embodiments, the solvent (5) can change from a liquidphase to a solid phase upon achievement of the preselected pressurethreshold.

As to particular embodiments, the solid phase of the solvent (5) canfacilitate or enable the interaction between the leuco dye (3) and thedeveloper (4), whereby the visibly colored dye-developer complex (7) canbe a crystalized structure having an extended conjugation of its πelectrons. Thus, upon achievement of the preselected pressure threshold,the visibly colored dye-developer complex (7) is formed, resulting inthe visible color change (6) which can be detected or visually observed.

In contrast, the liquid phase of the solvent (5), which can exist atpressures lesser than or below the preselected pressure threshold, canpreclude the interaction between the leuco dye (3) and the developer(4), rendering the leuco dye (3) colorless or substantially colorless.

Of note, because of the color-memory property of the color-changingsystem (2), after achievement of the preselected pressure threshold, thevisibly colored dye-developer complex (7) can remain stable even whenthe solvent (5) is in the liquid phase (for example, upon a decrease inpressure) until temperature T₂ is reached, as only a temperature equalto or above temperature T₂ inputs an amount of energy into the systemwhich is sufficient to destabilize the visibly colored dye-developercomplex (7).

Microcapsules

As stated above, the instant color-changing system (2) is contained,meaning that the dye (3), the developer (4), and the solvent (5) arecontinuously kept within a physical proximity which allows interactionbetween the compounds. Additionally, by being contained, thecolor-changing system (2) is separated from the external environment,which may damage or destroy the color-changing system (2).

Now referring primarily to FIG. 2A through FIG. 2C, as to particularembodiments, the color-changing system (2) can be encapsulated within acapsule or microcapsule (10) to provide a corresponding encapsulated ormicroencapsulated color-changing system (11), whereby the capsule ormicrocapsule (10) can have a diameter in a range of between about 300nanometers to about 100 microns, depending upon the embodiment.

The capsule or microcapsule wall (12) which forms the capsule ormicrocapsule (10) around the color-changing system (2) can be formedfrom any of a numerous and wide variety of polymers, such as melamineformaldehyde resin (CAS No.: 9003-08-01); polyurethane resin (CAS No.:9009-54-5); acrylic resin, or the like.

Of note, the capsule or microcapsule wall (12) need not rupture or burstfor the visible color change (6) to occur, which is in stark contrast toconventional pressure-indicating systems which require that theircapsule or microcapsule wall (12) rupture or burst for a visible colorchange (6) to occur. For example, a conventional pressure-indicatingsystem may include a color former and a color developer, at least one ofwhich is encapsulated to separate it from the other, thereby precludingthe color former and the color developer from interacting. Following,the capsule or microcapsule wall (12) must rupture or burst to permitthe color former and the color developer to be within a physicalproximity which allows interaction between the compounds, resulting in avisible color change (6). For example, upon rupturing or bursting of thecapsules or microcapsules, the color former is released therefrom,contacts and reacts with the color developer, and forms a coloredproduct which can be visually detected.

Said another way due to significance, it is not required or necessaryfor the capsule or microcapsule wall (12) which contains the instantcolor-changing system (2) to rupture or burst for the visibly coloreddye-developer complex (7) to form and correspondingly, for the visiblecolor change (6) to occur.

As to particular embodiments, it can be required that the capsule ormicrocapsule wall (12) does not rupture or burst for the visible colorchange (6) to occur. In other words, the visible color change (6) canonly occur if the capsule or microcapsule wall (12) remains intact,thereby functioning to contain the color-changing system (2).

Notably, because the capsule or microcapsule wall (12) which containsthe instant color-changing system (2) need not rupture for the visiblycolored dye-developer complex (7) to form, the visible color change (6)occurs whether the pressure applied to the encapsulated ormicroencapsulated color-changing system (11) is isotropic oranisotropic. This is another significant difference between the instantpressure sensor (1) and conventional pressure indicators which typicallychange color only upon the application of anisotropic pressure.

The properties of the capsule or microcapsule wall (12), such as itscomposition, rigidity, flexibility, wall thickness, size (correspondingto the diameter of the capsule or microcapsule), etc., can be chosen toresult in an encapsulated or microencapsulated color-changing system(11) which visibly changes color at the preselected pressure threshold,which can be chosen according to the particular circumstances, includingthe particular foodstuff being treated by HPP.

Coating

As to particular embodiments of the pressure sensor (1), theencapsulated or microencapsulated color-changing system (11) can beincorporated into a coating (13). As but one illustrative example, theencapsulated or microencapsulated color-changing system (11) can beincorporated into an ink (14).

As to particular embodiments, the ink (14) can be selected from thegroup including or consisting of: flexographic inks, gravure inks,offset inks, and screen inks. The ink (14) can be water-based,solvent-based, UV-curable, wet, dry, or combinations thereof, dependingupon the application.

As but only a few non-limiting examples for the purpose of illustration,the ink (14) can comprise: an acrylic solution; an acrylic emulsion; asulfonated polyester; or the like.

As to particular embodiments, the ink (14) can be specificallyformulated for application to a substrate (15) via printing, such asprinting onto a substrate (15) configured as packaging material designedfor HPP.

Substrate

As to particular embodiments of the pressure sensor (1), theencapsulated or microencapsulated color-changing system (11) can becoupled to a substrate (15), which can be formed from any of a numerousand wide variety of materials.

Importantly, the substrate (15) can, but need not necessarily, beflexible, meaning capable of being bent relatively easily, for examplemanually or by hand. This is in contrast to a rigid material, which isnot able to be bent easily or which is not able to be bent withoutbreaking. Of course, as to particular embodiments, the substrate (15)can be rigid without departing from the scope and spirit of theinvention.

Additionally, as to particular embodiments, the pressure sensor (1) can,but need not necessarily, further include a cover (16) which covers theencapsulated or microencapsulated color-changing system (11) coupled tothe substrate (15), thus disposing the encapsulated or microencapsulatedcolor-changing systems (11) between the substrate (15) and the cover(16).

The cover (16) may be used for aesthetic reasons or for safety reasons,for example when it is desirable to prevent contact between elements ofthe pressure sensor (1) and the foodstuff (9), either directly orthrough common contact with the working fluid of the HPP method. In someinstances, it may be desirable to prevent contact between theencapsulated or microencapsulated color-changing system (11) or thepressure sensor (1) and the working fluid by containing the pressuresensor (1) within a material that is substantially impermeable to theworking fluid, such as a waterproof or water-resistant material.

The precise shapes and conformations of the substrate (15) and the cover(16) are not critical. However, some embodiments lend themselves toeasier manufacture and assembly. For example, in one embodiment, thesubstrate (15) and the cover (16) have the form of a sheet (i.e., thesubstrate (15) and the cover (16) are configured as two sheets opposedadjacent one another). The substrate (15) and the cover (16) can haveapproximately the same thickness or different thicknesses, such as eachbeing a plastic film having a thickness of about 2 to 50 mils.

The materials from which each of the substrate (15) and the cover (16)are made is substantially immaterial, other than that substrate (15)should be sufficient to support the encapsulated or microencapsulatedcolor-changing system (11) and the cover (16) should be sufficient tocover the encapsulated or microencapsulated color-changing system (11).By way of example, each of the substrate (15) and the cover (16) can bea polyester film having a thickness of about 2 to 10 mils. Preferably,at least one of the substrate (15) and the cover (16) is transparent.

At least one of the substrate (15) and the cover (16) can have a viewingportion adapted to permit detection of the visible color change (6)associated with formation of the visibly colored dye-developer complex(7), for example by visual observation of the pressure sensor (1) (i.e.,not requiring disassembly of the pressure sensor (1)). Alternatively,the pressure sensor (1) can be disassembled to determine whether thevisibly colored dye-developer complex (7) formed. As to particularembodiments, at least one of the substrate (15) and the cover (16) issufficiently transparent or translucent that the visible color change(6) associated with formation of the visibly colored dye-developercomplex (7) can be detected by direct visual observation of the viewingportion.

As to particular embodiments, one or both of the substrate (15) andcover (16) can act as a packaging material or package, or a componentthereof, for containing a foodstuff (9). The substrate (15), the cover(16), or both can be an integral part of the packaging material (i.e.,unitary with the packaging material such that removal of the substrate(15) or the cover (16) would compromise the integrity of the packagingmaterial and its function of separating its interior from the externalenvironment). Alternatively, the substrate (15), the cover (16), or bothcan be separable (e.g., tearable, detachable, or peelable) from thepackaging material.

If only one of the substrate (15) and the cover (16) is a part of thepackaging material, the pressure sensor (1) device can be preferablyconfigured such that no fluid communication occurs between theencapsulated or microencapsulated color changing system (11) and thecavity of the packaging material containing the foodstuff (9) when thepackaging material is intact. Such a configuration reduces thelikelihood that capsules or microcapsules (10) or the components of thecolor-changing system (2) contained within the capsules or microcapsules(10) will contact a foodstuff (9) packed within the packaging material.

As to particular embodiments, the capsules or microcapsules (10) whichcontain the color-changing system (2) can be bound to the substrate(15), to the cover (16), or to both, either directly or by way of abinding agent.

Alternatively, as to other particular embodiments, the capsules ormicrocapsules (10) which contain the color-changing system (2) can bekept proximate to, but not necessarily bound to any surface of, thesubstrate (15) or the cover (16).

Range of Preselected Pressure Thresholds

The dye (3) and the developer (4) of the instant containedcolor-changing system (2) can interact to form the visibly coloreddye-developer complex (7) and provide a visible color change (6) uponthe achievement of any of a numerous and wide variety of preselectedpressure thresholds, depending upon the application. For example, thepreselected pressure threshold can be in a range of between at leastabout 10,000 psi to about 100,000 psi.

As to particular embodiments, the preselected pressure threshold can beabout 10,000 psi or at least about 10,000 psi; correspondingly, the dye(3) and the developer (4) can interact to form the visibly coloreddye-developer complex (7) and provide a visible color change (6) whenexposed to a pressure of about 10,000 psi or at least about 10,000 psi,thereby indicating that the pressure sensor (1) and any foodstuff (9)with which it is reliably associated have been exposed to a pressure ofabout 10,000 psi or at least about 10,000 psi.

As to particular embodiments, the preselected pressure threshold can beabout 20,000 psi or at least about 20,000 psi; correspondingly, the dye(3) and the developer (4) can interact to form the visibly coloreddye-developer complex (7) and provide a visible color change (6) whenexposed to a pressure of about 20,000 psi or at least about 20,000 psi,thereby indicating that the pressure sensor (1) and any foodstuff (9)with which it is reliably associated have been exposed to a pressure ofabout 20,000 psi or at least about 20,000 psi.

As to particular embodiments, the preselected pressure threshold can beabout 30,000 psi or at least about 30,000 psi; correspondingly, the dye(3) and the developer (4) can interact to form the visibly coloreddye-developer complex (7) and provide a visible color change (6) whenexposed to a pressure of about 30,000 psi or at least about 30,000 psi,thereby indicating that the pressure sensor (1) and any foodstuff (9)with which it is reliably associated have been exposed to a pressure ofabout 30,000 psi or at least about 30,000 psi.

As to particular embodiments, the preselected pressure threshold can beabout 40,000 psi or at least about 40,000 psi; correspondingly, the dye(3) and the developer (4) can interact to form the visibly coloreddye-developer complex (7) and provide a visible color change (6) whenexposed to a pressure of about 40,000 psi or at least about 40,000 psi,thereby indicating that the pressure sensor (1) and any foodstuff (9)with which it is reliably associated have been exposed to a pressure ofabout 40,000 psi or at least about 40,000 psi.

As to particular embodiments, the preselected pressure threshold can beabout 50,000 psi or at least about 50,000 psi; correspondingly, the dye(3) and the developer (4) can interact to form the visibly coloreddye-developer complex (7) and provide a visible color change (6) whenexposed to a pressure of about 50,000 psi or at least about 50,000 psi,thereby indicating that the pressure sensor (1) and any foodstuff (9)with which it is reliably associated have been exposed to a pressure ofabout 50,000 psi or at least about 50,000 psi.

As to particular embodiments, the preselected pressure threshold can beabout 60,000 psi or at least about 60,000 psi; correspondingly, the dye(3) and the developer (4) can interact to form the visibly coloreddye-developer complex (7) and provide a visible color change (6) whenexposed to a pressure of about 60,000 psi or at least about 60,000 psi,thereby indicating that the pressure sensor (1) and any foodstuff (9)with which it is reliably associated have been exposed to a pressure ofabout 60,000 psi or at least about 60,000 psi.

As to particular embodiments, the preselected pressure threshold can beabout 70,000 psi or at least about 70,000 psi; correspondingly, the dye(3) and the developer (4) can interact to form the visibly coloreddye-developer complex (7) and provide a visible color change (6) whenexposed to a pressure of about 70,000 psi or at least about 70,000 psi,thereby indicating that the pressure sensor (1) and any foodstuff (9)with which it is reliably associated have been exposed to a pressure ofabout 70,000 psi or at least about 70,000 psi.

As to particular embodiments, the preselected pressure threshold can beabout 80,000 psi or at least about 80,000 psi; correspondingly, the dye(3) and the developer (4) can interact to form the visibly coloreddye-developer complex (7) and provide a visible color change (6) whenexposed to a pressure of about 80,000 psi or at least about 80,000 psi,thereby indicating that the pressure sensor (1) and any foodstuff (9)with which it is reliably associated have been exposed to a pressure ofabout 80,000 psi or at least about 80,000 psi.

As to particular embodiments, the preselected pressure threshold can beabout 90,000 psi or at least about 90,000 psi; correspondingly, the dye(3) and the developer (4) can interact to form the visibly coloreddye-developer complex (7) and provide a visible color change (6) whenexposed to a pressure of about 90,000 psi or at least about 90,000 psi,thereby indicating that the pressure sensor (1) and any foodstuff (9)with which it is reliably associated have been exposed to a pressure ofabout 90,000 psi or at least about 90,000 psi.

As to particular embodiments, the preselected pressure threshold can beabout 100,000 psi or at least about 100,000 psi; correspondingly, thedye (3) and the developer (4) can interact to form the visibly coloreddye-developer complex (7) and provide a visible color change (6) whenexposed to a pressure of about 100,000 psi or at least about 100,000psi, thereby indicating that the pressure sensor (1) and any foodstuff(9) with which it is reliably associated have been exposed to a pressureof about 100,000 psi or at least about 100,000 psi.

As but one non-limiting example, the preselected pressure threshold canbe about 87,000 psi; correspondingly, the dye (3) and the developer (4)can interact to form the visibly colored dye-developer complex (7) andprovide a visible color change (6) when exposed to a pressure of about87,000 psi, thereby indicating that the pressure sensor (1) and anyfoodstuff (9) which it is reliably associated with have been exposed toa pressure of at least about 87,000 psi.

As to particular embodiments, the pressure sensor (1) can include aplurality of populations of encapsulated or microencapsulatedcolor-changing systems (11), whereby each population has acharacteristic preselected pressure threshold to which it reacts toprovide a visible color change (6).

As but one illustrative example, a first population of encapsulated ormicroencapsulated color-changing systems (11) can provide a visiblecolor change (6) at a relatively low preselected pressure threshold(e.g., 15,000 psi) and a second population of encapsulated ormicroencapsulated color-changing systems (11) can provide a visiblecolor change (6) at a relatively high preselected pressure threshold(e.g., 87,000 psi), whereby the first and second populations can havethe same or different dyes contained within them.

As but a second illustrative example, a plurality of populations ofencapsulated or microencapsulated color-changing systems (11), eachhaving a characteristic preselected pressure threshold to which itreacts to provide a visible color change (6), can be disposed in anarrangement that facilitates observation of their color development,such as by arranging the populations sequentially in order of increasingpreselected pressure threshold and by including indicia on or within thepressure sensor (1) that correlates color development of the populationswith their associated preselected pressure threshold.

Additional Indicators

As to particular embodiments, the instant pressure sensor (1) caninclude other indicators (e.g., a temperature indicator or a moisturesensor) associated with it, so that the pressure-sensing functionalityof the pressure sensor (1) can be combined with (for example)temperature-sensing functionality or moisture-sensing functionality.

Use of the Pressure Sensor

The instant pressure sensor (1) can be used with a method for visuallydetermining whether a preselected pressure threshold has been achieved,for example during HPP treatment of a foodstuff (9). Also, the instantpressure sensor (1) can be used with a method for indicating orconfirming achievement of a preselected pressure threshold, for exampleduring HPP treatment of a foodstuff (9).

Each method includes reliably associating the pressure sensor (1) with afoodstuff (9). Further, each method can, but need not necessarily,include subjecting the foodstuff (9) and reliably associated pressuresensor (1) to HPP treatment. Further, each method can, but need notnecessarily, include detecting whether or not the visible color change(6) occurred. As to particular embodiments, detecting whether or not thevisible color change (6) occurred can include visually observing thepressure sensor (1).

Following, detection of the visible color change (6), for example byvisual observation, can indicate that the preselected pressure thresholdwas achieved during HPP treatment. In contrast, detection of the absenceof the visible color change (6), for example by visual observation, canindicate that the preselected pressure threshold was not achieved duringHPP treatment.

The pressure sensor (1) can be reliably associated with a singlefoodstuff (9), a single package, a plurality of foodstuffs (9), or aplurality of packages. The method by which the pressure sensor (1) andthe foodstuff (9) are reliably associated is not critical andpractically any method of association that will retain association ofthe pressure sensor (1) and foodstuff(s) (9) during HPP treatment can beused.

By way of non-limiting example, the pressure sensor (1) can simply beplaced loose in the vessel (8) used for HPP treatment and left therewith the foodstuff (9) until dissociation is desired. However, it istypically preferable that the pressure sensor (1) remain associated withthe foodstuff (9) following HPP treatment. To achieve this end, thepressure sensor (1) and foodstuff (9) can be associated in any way andusing any devices typically used in the food processing industry. By wayof non-limiting examples, the pressure sensor (1) can be adhered to,glued, tied, or otherwise attached to the foodstuff (9), packagingmaterial, or package or to a container or rack that contains thefoodstuff (9), packaging material, or package.

The pressure sensor (1) can be co-packaged with the foodstuff (9) orused to seal a package or container containing the foodstuff (9), suchthat the foodstuff (9) cannot be removed from the package or containerwithout removing or breaking the pressure sensor (1). Likewise, thepressure sensor (1) can be part of, or contained within, a package usedfor commercial shipment, display, or sale of the foodstuff (9). By wayof non-limiting example, the pressure sensor (1) can be sandwichedbetween two layers of flexible plastic film that are used to seal afoodstuff (9) for retail sale. In such an arrangement, the pressuresensor (1) is preferably sealed in a compartment distinct from (notfluidly communicable with) the compartment in which the foodstuff (9) issealed.

By reliably associating the pressure sensor (1) and the foodstuff (9),the information displayed by the pressure sensor (1) (i.e., whether ornot the preselected pressure threshold was achieved during HPPtreatment) can remain associated with the foodstuff (9) and informdownstream users of the foodstuff (9) (i.e., food processing plantworkers, retailers, or customers) regarding the HPP treatment status ofthe foodstuff (9).

Example 1

The subject matter of this disclosure is now described with reference tothe following example. Of note, this example is provided for the purposeof illustration only, and the subject matter is not limited to thisexample, but rather encompasses all variations which are evident as aresult of the teaching provided herein.

In order to test whether a particular embodiment of the instant pressuresensor (1) described herein could be used for visually determiningwhether a preselected pressure threshold has been achieved during HPPtreatment or for indicating achievement of a preselected pressurethreshold during HPP treatment, a pressure sensor (1) was developed andtested in a model HPP system.

The pressure sensor (1) included a microencapsulated thermochromiccolor-changing system (11) having the color-memory property as describedabove, comprising about 5-10% w/w7-[4-(diethylamino)-2-ethoxyphenyl]-7-(1-ethyl-2-methylindol-3-yl)furo[3,4-b]pyridin-5-one(CAS No.: 69898-40-4) as the dye, about 10-20% w/w4-[2-(4-hydroxyphenyl)-4-methylpentan-2-yl]phenol (CAS No.: 6807-17-6)as the developer, and about 70-85% w/w dodecanophenone (CAS No.:1674-38-0) as the solvent, whereby the microencapsulated thermochromiccolor-changing system (11) was prepared as taught in U.S. Pat. Nos.8,883,049, 9,175,175, and 9,695,320, each of which is herebyincorporated by reference herein.

The microencapsulated thermochromic color-changing system (11) wasincorporated into an ink including JONCRYL® 142 (available from BASF)and SURFYNOL® 104 (available from Air Products). Following, theformulation was printed onto a substrate (15) configured aspolypropylene film to provide the pressure sensor (1) for testing.

Following, each of five distinct pressure sensors (1) was coupled to acontainer to provide a pressure sensor-container construct which wasthen disposed/placed in a vessel (8) and subjected to HPP treatment,whereby each of the five distinct pressure sensor-container constructswas subjected to a different preselected pressure threshold (as shown inTable 1). Of note, the vessel (8) within which each pressuresensor-container construct was disposed/placed had an initialtemperature of about 15° Celsius when at atmospheric pressure.Subsequent to achievement of each preselected pressure threshold, thevessel (8) was depressurized and returned to atmospheric pressure, andthe effect on each pressure sensor (1) was observed.

The results of the testing are shown in Table 1, whereby no color changewas observed at 15,000 psi but a visible color change (6) was observedupon achievement of 25,000 psi, 35,000 psi, 45,000 psi, and 85,000 psi.Additionally, FIG. 4 is a photograph showing (i) no color change ofSample 1 and (ii) the visible color change (6) from colorless orsubstantially colorless to blue of Samples 2 through 5 upon achievementof their respective preselected pressure thresholds.

TABLE 1 Preselected Observation of Sample Pressure Threshold VisibleColor Number (psi) Change 1 15,000 no 2 25,000 yes 3 35,000 yes 4 45,000yes 5 85,000 yes

From the observations described and shown in this example, it wasconcluded that the instant pressure sensor (1) is suitable (i) forvisually determining whether a preselected pressure threshold has beenachieved during HPP treatment, and (ii) for indicating achievement of apreselected pressure threshold during HPP treatment.

Temperature of HPP Treatment

During HPP treatment, variable conditions include pressure as well astemperature. It should be appreciated that noted herein, the preselectedpressure threshold of the color-changing system (2), which is thepressure at which the dye (3) and the developer (4) interact to form thevisibly colored dye-developer complex (7), can be adjusted by alteringthe temperature of the HPP treatment. For example, by increasing thetemperature of the HPP treatment, the preselected pressure threshold towhich the color-changing system (2) reacts can be correspondinglyincreased. Conversely, by decreasing the temperature of the HPPtreatment, the preselected pressure threshold to which thecolor-changing system (2) reacts can be correspondingly decreased.

Moreover, during HPP treatment, in addition to an increase in pressure,an increase in temperature may also be observed, which is an adiabaticprocess. For example, it may be expected that during HPP, adiabaticcompression of water increases the temperature of the system by about 3Celsius degrees for every 14,500 psi increase in pressure.

Following, consideration should be paid to the maximum temperaturereached within the vessel (8) during HPP treatment to ensure that themaximum pressure does not equal or exceed T₂, at which point asufficient amount of energy is input into the system to destabilize thevisibly colored dye-developer complex (7).

As can be easily understood from the foregoing, the basic concepts ofthe present invention may be embodied in a variety of ways. Theinvention involves numerous and varied embodiments of a pressure sensorand methods for making and using such a pressure sensor.

As such, the particular embodiments or elements of the inventiondisclosed by the description or shown in the figures or tablesaccompanying this application are not intended to be limiting, butrather exemplary of the numerous and varied embodiments genericallyencompassed by the invention or equivalents encompassed with respect toany particular element thereof. In addition, the specific description ofa single embodiment or element of the invention may not explicitlydescribe all embodiments or elements possible; many alternatives areimplicitly disclosed by the description and figures.

It should be understood that each element of an apparatus or each stepof a method may be described by an apparatus term or method term. Suchterms can be substituted where desired to make explicit the implicitlybroad coverage to which this invention is entitled. As but one example,it should be understood that all steps of a method may be disclosed asan action, a means for taking that action, or as an element which causesthat action. Similarly, each element of an apparatus may be disclosed asthe physical element or the action which that physical elementfacilitates. As but one example, the disclosure of a “combination”should be understood to encompass disclosure of the act of“sensing”—whether explicitly discussed or not—and, conversely, werethere effectively disclosure of the act of “sensing”, such a disclosureshould be understood to encompass disclosure of a “sensor” and even a“means for sensing”. Such alternative terms for each element or step areto be understood to be explicitly included in the description.

In addition, as to each term used it should be understood that unlessits utilization in this application is inconsistent with suchinterpretation, common dictionary definitions should be understood to beincluded in the description for each term as contained in the RandomHouse Webster's Unabridged Dictionary, second edition, each definitionhereby incorporated by reference.

All numeric values herein are assumed to be modified by the term“about”, whether or not explicitly indicated. For the purposes of thepresent invention, ranges may be expressed as from “about” oneparticular value to “about” another particular value. When such a rangeis expressed, another embodiment includes from the one particular valueto the other particular value. The recitation of numerical ranges byendpoints includes all the numeric values subsumed within that range. Anumerical range of one to five includes for example the numeric values1, 1.5, 2, 2.75, 3, 3.80, 4, 5, and so forth. It will be furtherunderstood that the endpoints of each of the ranges are significant bothin relation to the other endpoint, and independently of the otherendpoint. When a value is expressed as an approximation by use of theantecedent “about,” it will be understood that the particular valueforms another embodiment. The term “about” generally refers to a rangeof numeric values that one of skill in the art would consider equivalentto the recited numeric value or having the same function or result.Similarly, the antecedent “substantially” means largely, but not wholly,the same form, manner or degree and the particular element will have arange of configurations as a person of ordinary skill in the art wouldconsider as having the same function or result. When a particularelement is expressed as an approximation by use of the antecedent“substantially,” it will be understood that the particular element formsanother embodiment.

Moreover, for the purposes of the present invention, the term “a” or“an” entity refers to one or more of that entity unless otherwiselimited. As such, the terms “a” or “an”, “one or more” and “at leastone” can be used interchangeably herein.

Thus, the applicant(s) should be understood to claim at least: i) eachof the pressure sensors herein disclosed and described, ii) the relatedmethods disclosed and described, iii) similar, equivalent, and evenimplicit variations of each of these devices and methods, iv) thosealternative embodiments which accomplish each of the functions shown,disclosed, or described, v) those alternative designs and methods whichaccomplish each of the functions shown as are implicit to accomplishthat which is disclosed and described, vi) each feature, component, andstep shown as separate and independent inventions, vii) the applicationsenhanced by the various systems or components disclosed, viii) theresulting products produced by such systems or components, ix) methodsand apparatuses substantially as described hereinbefore and withreference to any of the accompanying examples, x) the variouscombinations and permutations of each of the previous elementsdisclosed.

The background section of this patent application, if any, provides astatement of the field of endeavor to which the invention pertains. Thissection may also incorporate or contain paraphrasing of certain UnitedStates patents, patent applications, publications, or subject matter ofthe claimed invention useful in relating information, problems, orconcerns about the state of technology to which the invention is drawntoward. It is not intended that any United States patent, patentapplication, publication, statement or other information cited orincorporated herein be interpreted, construed or deemed to be admittedas prior art with respect to the invention.

The claims set forth in this specification, if any, are herebyincorporated by reference as part of this description of the invention,and the applicant expressly reserves the right to use all of or aportion of such incorporated content of such claims as additionaldescription to support any of or all of the claims or any element orcomponent thereof, and the applicant further expressly reserves theright to move any portion of or all of the incorporated content of suchclaims or any element or component thereof from the description into theclaims or vice-versa as necessary to define the matter for whichprotection is sought by this application or by any subsequentapplication or continuation, division, or continuation-in-partapplication thereof, or to obtain any benefit of, reduction in feespursuant to, or to comply with the patent laws, rules, or regulations ofany country or treaty, and such content incorporated by reference shallsurvive during the entire pendency of this application including anysubsequent continuation, division, or continuation-in-part applicationthereof or any reissue or extension thereon.

Additionally, the claims set forth in this specification, if any, arefurther intended to describe the metes and bounds of a limited number ofthe preferred embodiments of the invention and are not to be construedas the broadest embodiment of the invention or a complete listing ofembodiments of the invention that may be claimed. The applicant does notwaive any right to develop further claims based upon the description setforth above as a part of any continuation, division, orcontinuation-in-part, or similar application.

1-147. (canceled)
 148. A pressure sensor for visually determiningwhether a pressure threshold has been achieved, said pressure sensorcomprising: a color-changing system comprising: a dye; a developer; anda solvent; wherein said color-changing system is contained such thatsaid dye, said developer, and said solvent are encapsulated together;wherein said developer variably interacts with said dye according to thepressure of said color-changing system; and wherein upon achievement ofsaid pressure threshold, said dye and said developer interact, resultingin a visible color change.
 149. The pressure sensor of claim 148,wherein said dye comprises a leuco dye.
 150. The pressure sensor ofclaim 149, wherein said leuco dye changes between a substantiallycolorless state and a visibly colored state.
 151. The pressure sensor ofclaim 150, wherein upon achievement of said pressure threshold, saidleuco dye changes from said substantially colorless state to saidvisibly colored state.
 152. The pressure sensor of claim 151, whereinsaid visibly colored state is retained upon said decrease in pressurefrom said pressure threshold.
 153. The pressure sensor of claim 148,wherein said color-changing system is encapsulated within a capsule toprovide an encapsulated color-changing system.
 154. The pressure sensorof claim 153, wherein said color-changing system is encapsulated withina microcapsule to provide a microencapsulated color-changing system.155. The pressure sensor of claim 154, wherein upon achievement of saidselected pressure threshold, said microcapsule need not rupture toproduce said visible color change.
 156. The pressure sensor of claim154, wherein upon achievement of said selected pressure threshold, saidvisible color change occurs within said microcapsule.
 157. The pressuresensor of claim 148, wherein said color-changing system is incorporatedinto a coating.
 158. The pressure sensor of claim 148, wherein saidcolor-changing system is incorporated into an ink.
 159. The pressuresensor of claim 148, wherein said coloring-changing system comprises areversible color-changing system.
 160. The pressure sensor of claim 148,wherein said color-changing system comprises a thermochromiccolor-changing system.
 161. The pressure sensor of claim 148, whereinsaid color-changing system comprises a color-memory property whichfacilitates retention of said visible color change upon a decrease inpressure from said pressure threshold to record said achievement of saidpressure threshold.
 162. A method for visually determining whether apressure threshold has been achieved during high pressure processingtreatment of a foodstuff, comprising: reliably associating a pressuresensor with said foodstuff, said pressure sensor comprising: acolor-changing system comprising: a dye; a developer; and a solvent;wherein said color-changing system is contained such that said dye, saiddeveloper, and said solvent are encapsulated together; wherein saiddeveloper variably interacts with said dye according to the pressure ofsaid color-changing system; and wherein upon achievement of saidpressure threshold, said dye and said developer interact, resulting in avisible color change.
 163. The method of claim 162, wherein saidcoloring-changing system comprises a reversible color-changing system.164. The method of claim 162, wherein said color-changing systemcomprises a thermochromic color-changing system.
 165. The method ofclaim 162, wherein said color-changing system comprises a color-memoryproperty which facilitates retention of said visible color change upon adecrease in pressure from said pressure threshold to record saidachievement of said pressure threshold.
 166. A method for indicatingachievement of a pressure threshold during high pressure processingtreatment of a foodstuff, comprising: reliably associating a pressuresensor with said foodstuff, said pressure sensor comprising: acolor-changing system comprising: a dye; a developer; and a solvent;wherein said color-changing system is contained such that said dye, saiddeveloper, and said solvent are encapsulated together; wherein saiddeveloper variably interacts with said dye according to the pressure ofsaid color-changing system; and wherein upon achievement of saidpressure threshold, said dye and said developer interact, resulting in avisible color change.
 167. The method of claim 166, wherein saidcoloring-changing system comprises a reversible color-changing system.168. The method of claim 166, wherein said color-changing systemcomprises a thermochromic color-changing system.
 169. The method ofclaim 166, wherein said color-changing system comprises a color-memoryproperty which facilitates retention of said visible color change upon adecrease in pressure from said pressure threshold to record saidachievement of said pressure threshold.